Soft magnetic ferrite bodies of high permeability and small hysteresis losses



Oct. 8, 1963 TSUNEO AKASHI ETAL 3,

SOFT MAGNETIC FERRITE BODIES OF HIGH PERMEABILITY AND SMALL HYSTERESISLOSSES Filed Jan. 17, 1961 5 Sheets-Sheet 1 AKASHI TOBITA TAKAHASHITAKAMIZAWA INVENTORS 2;," PMM A 7' TORNEYS Oct. 8, 1963 TSUNEO AKASHIETAL 3, 0

SOFT MAGNETIC FERRITE BODIES OF HIGH PERMEABILITY AND SMALL HYSTERESISLOSSES Filed Jan. 17, 1961 5 Sheets-Sheet 2 6 0.! 0.2 as 04 0.5 0.6 07a8 09 I0 9 AKASHI TOBITA TAKAHASHI TAKAMIZAWA INVENTORS A frame-r5 Oct.8, 1963 SOFT MAGNETIC FERRITE BODIES OF HIGH PERMEABILITY 7 Filed Jan.17, 1961 TSUNEO AKASHI ETAL 3,106,534"

AND SMALL HYSTERESIS LOSSES 5 Sheets-Shee t 3 02 as 05 "A AKASHI TOBITATAKAHASHI TAKAMIZAWA INVENTORS ATTORNEYS Oct. 8, 1963 TSUNEO AKASHI ETAL3,106,534 SOFT MAGNETIC FERRITE BODIES OF HIGH PERMEABILITY AND SMALLHYSTERESIS LOSSES Filed Jan. 17, 1961 5 Sheets-Sheet 4 AKA'SHI TOBITATAKAHASHI' TAKAMIZAWA INVENTORS Fina TSUNEO AKASHI ETAL 3,106,534 SOFTMAGNETIC FERRITE BODIES OF HIGH PERMEABILITY AND SMALL HYSTERESIS LOSSESFiled Jan. 17, 1961 5 Sheets-Sheet 5 T. AKASHI M. TOBITA H. TAKAHASHI 00.0! 0-02 0.03 004 0.05 0.06 007 0.00 0.09 0.; g TAKAMIZA A INVENTORSATTORNEYS United States Patent Office 3,106,534 Patented Oct. 8, 1963 3106 534 SOFT MAGNETIC F ERITE BQDIES F HEGH PERMEABILEIY AND SMALLHYSTERESHS LOSSES Tsuneo Akashi, Masao Tobita, Masao Takahashi, and

Hideo Takamizawa, all of Tokyo, Japan, assignors to Nippon ElectricCompany, Ltd, Tokyo, Japan, a corporation of Japan Filed fan. 17, 1961,Ser. No. 83,332 Claims priority, application Japan Jan. 26, 1960 6Claims. (til. 252-625) This application is a continuationin-part of ourappli cation Serial No. 4,728, filed January 26, 1960, and nowabandoned.

This invention relates to soft magnetic ferrite material, and moreparticularly to such ferrite material especially adapted for use inelectrical communication apparatus. As used herein, sof ferrite materialmeans magnetic ferrite material of low magnetic retentivity.

As is known, manganese-zinc ferrites have desirable high-permeabilitycharacteristics for the communication field. To secure optimum operatingresults in the cornmunication field, it is essential that such softmanganesezinc ferrites shall combine (1) the highest possiblepermeability with (2) the lowest possible hysteresis losses. Herctofore,the permeability of such ferrites was increased by providing acomposition of a low Curie point and by raising its sinteringtemperature. However, lowering of the Curie point of such ferritecomposition restricts the range of its operating temperature, and anincrease of its sintering temperature raises its hysteresis losses.Heretofore, manganese-zinc ferrites of best operating characteristicshave been obtained by making them with the highest degree of purity.However, although such high-purity ferrites exhibit increasedpermeability, their hysteresis losses are not decreased, and remainexcessive.

An object of the present invention is to obtain a soft magnetic materialwhich combines high permeability with an extremely low hysteresis loss.

A further object of this invention is to obtain manganese-zinc ferritesexhibiting a lower 1///.Q than heretofore obtainable.

According to the invention, soft ferrite bodies of compositionsconsisting of,

M01 percent are given highest permeability and lowest hysteresis losses,by embodying in the composition 0.05% to 0.3% by weight of calcium oxidetogether with 0.005% to 0.035 by weight of silicon dioxide.

Throughout the specification and claims, all proportions are given byweight unless otherwise specified.

The objects of the present invention and the manner of attaining thesame, will be more fully explained in the following description thereof,in which experimental results with conventional ferrites and withferrites of the invention are given with reference to the accompanyingdrawings, in which:

FIG. 1 shows characteristic curves of the efiiect of calcium oxideadditions only on the DC. specific resistance of a manganese-Zincferrite within the above-specified range;

FIG. 2 shows characteristic curves of the effect of calcium oxideadditions only on the Q of such ferrite at 100 kilocycles per second;

FIG. 3 shows characteristic curves of the effect of calcium oxideadditions on the ,u. of such ferrite;

FIG. 4 shows characteristic curves of the effect of calcium oxideadditions only on l/,uQ of such ferrite;

FIG. 5 shows characteristic curves of the effect of the combinedadditions of both silicon dioxide and calcium oxide on the specificelectric resistance of such ferrite;

FIG. 6 shows characteristic curves of the effect of silicon dioxideadditions only on the specific D.C.electric resistance of such ferrite;

FIG. 7 shows characteristic curves of the efiectof combined additions ofsilicon dioxide and calcium oxide on the Q of such ferrite;

FIG. 8 shows characteristic curves of the effect of silicon dioxideadditions only on the Q of such ferrite;

FIG. 9 shows characteristic curves of the effect of the combinedadditions of both silicon dioxide and calcium oxide on the permeabilityof such ferrite;

FIG. 10 shows characteristic curves of the effect of silicon dioxideadditions only on the ,u of such ferrite;

FIG. 11 shows characteristic curves of the effect of combined additionof both silicon dioxide and calcium oxide on l/,u,Q of such ferrite; and

FIG. 12 shows a characteristic curve showing the effect of silicondioxide additions only on 1/p.Q of such ferrite.

In order to show the results of high purification mentioned above, aseries of experiments have been carried out. The row materials used inthe experiments are as followings: iron oxide (manganese, zinc, andcopper: below 0.001%; other impurities, not detectable) manu factored bythermal decomposition of ferrous oxalate which is obtained by dissolvingelectrolytic iron in special-grade sulfuric acid and then precipitatingwith special-grade ammonium oxalate; manganese carbonate (iron, zinc,copper, calcium and magnesium: below 0.001%; other impurities, notdetectable) produced by dissolving electrolytic manganese intospecial-grade sulfuric acid and then precipitating with special-gradeammonium carbonate; and special-grade zinc oxide. The impurities in MnOand ZnO and of the manufacturing processes, were kept to a minimum. Someof the results are shown in Table 1.

Table I n (3 milli-oersteds, kc.) Q (3 milli-oersteds, 100 kc.) H (10-30rni11ioersteds, 100 kc.) l/nQ (3 milli-oersteds, 100 kc.)

Sinterlng temperature 1,200 O. (in nitrogen gas) t 1,250 O. (in nitrogengas) Composition I Characteristic l /HQ h I H 2 Q X10 X10 Q X100 35;Z11O11.- 2,000 4. 5 107 2, 560 2, 450 3. 7 110 2,670 F0203, 32.6;

M110, 27; ZnO, 24.4 (in mol percent) 2,500 4 100 1, 425 3, 650 3. 3 831,420

H denotes hysteresis loss in the following Jordans formula:

R/L= H.NI/l.(f/800) +Fn(800) +t(f/800) where, R: Total loss L:Inductance N: Total turns I: Electric current made to flow through thewinding (A) l: Length of the magnetic path cm.)

7: Frequency (c./s.)

Fn: Eddy current loss t: Residual loss As shown in the table,manganese-zinc ferrites having high permeabilities as compared withmanganese-zinc ferrites now on the market, are easily obtained bysintering at low temperatures. The electrical resistance, however, isextremely small, the specific resistance being 1-2 ohmcm. As a result,the eddy current loss becomes large, and the value of 1/,uQ at 100 kc.is extremely large. Therefore, these ferrites can scarcely be used in amagnetic core for high-frequency use.

In order to prevent the lowering of Q, it has already been proposed toadd calcium oxide to high-purity raw materials. It is alleged that aspecific resistance of several hundred ohm-centimeters may thereby beattained. According to our experiments, however, the results of theaddition of calcium oxide to the above-mentioned high-purity rawmaterials, are not favorable. In our experiments, 1% calcium oxide wasadded to the highly pure raw materials of a composition consisting offerric oxide 54 mol percent, manganese oxide 35 mol percent, and zincoxide 11 mol percent, and the ferrite was sintered in a highly purenitrogen atmosphere at 1200 C. for four hours. The sintered ferrite wasthen cooled to 400 C. for nine hours in an oven, and thereafter cooledin air to normal temperature. The effect of the addition of calciumoxide on the specified electrical resistance is, as shown in FIG. 1,comparatively small. Although the addition of calcium oxide is more orless effective with respect to Q at 3 milli-oersted and 100 kc., asshown in FIG. 2, it shows a detrimental effect on ,u. at 3 milli-oerstedand 100 kc., as shown in FIG. 3. Although the value of 1/,u.Q at 3milli-oersteds and 100 kc. has been improved to a certain extent ascompared with that of a ferrite in which calcium oxide is not added, thevalue still fails in satisfying the characteristics required inpresent-day communication apparatus, as shown in FIG. 4.

According to our other experiments which were carried out in a similarmanner, and by adding, in place of calcium oxide, in an amount of0.011%, one of the oxides of lithium, sodium, potassium, copper,beryllium, magnesium, strontium, cadmium, barium, boron, aluminum,yttrium, indium, lanthanum, cerium, samarium, silicon, titanium,germanium, zirconium, tin, lead, thorium, vanadium, arsenic, niobium,antimony, tantalum, bismuth, chromium, molybdenum, tungsten, cobalt, andnickel, it has been found, however, that the value of l/ Q could not beimproved to a large extent by the addition of only one of the oxides.

This invention resulted from various types of experiments to minimizethe value of 1/ Q, while preserving the excellent characteristics of ahigh-purity material, through the effect of combined addition ofrelatively small amounts of more than two kinds of addition materials.The invention will now be more fully described by reference to examplesthereof.

By way of example, the experimental results of the effect of a combinedaddition of a small quantity of calcium oxide and a trace of silicondioxide on a manganese-zinc ferrite, will be described for the casewhere 01-07% of calcium oxide and 0.0l-0.07% of silicon dioxide is addedto the composition of the above-mentioned highly pure raw materialsconsisting of ferric oxide 54 mol percent, manganese oxide 35 molpercent, and zinc oxide 11 mol percent, and as prepared in the mannermentioned above, and where the ferrite of the above-mentionedcomposition is sintered at 1200" C. in an atmosphere of nitrogen ofextremely high purity, for four hours. The sintered ferrite was thencooled to 400 C. for nine hours in an oven, and thereafter cooled in airto normaltemperature. Also, experimental results will be described toshow the effect of the addition of a trace of silicon dioxide on amanganese ferrite which comprises as the main components theabove-mentioned highly pure ferric oxide 54 mol percent, manganese oxide4 35 mol percent, and zinc oxide 11 mol percent, and as the auxiliarycomponent, 00.1% of silicon dioxide, and which is sintered at 1200 C. inan atmosphere of highly pure nitrogen, for four hours.

As shown in FIG. 5, which shows variation of specific electricalresistance for various contents of calcium oxide and silicon dioxide, itwill be evident that the combined effect of a small quantity of calciumoxide and a trace of silicon dioxide is extremely powerful on thespecific electrical resistance of the manganese-zinc ferrite, whencompared with FIGS. 1 and 6, which show the effects of adding calciumoxide only, and silicon dioxide only, to the same main composition,respectively.

As shown in FIG. 7, which shows variation in a at 3 milli-oersteds andkc. due to combined addition of calcium oxide and silicon dioxide invarious amounts, it will be readily seen that the combined effect of asmall quantity of calcium oxide and a trace of silicon dioxide iseffective, as compared with FIGS. 2 and 8, which show the effects ofadding only either calcium oxide or silicon dioxide, respectively, tothe same main composition. Although a high value of Q is obtained, asshown in FIG. 2, by the addition of calcium oxide only, lowering in thevalue of a is considerable, as mentioned previously, with the resultthat favorable characteristics of 1/ .Q are not obtainable in this case.According to the present invention, sufficiently high Q characteristicscan be obtained even in a range in which the addition of calcium oxideis so small that the lowering in the value of can hardly be observed. Asa result, it is possible, according to this invention, to prepare amanganese-zinc ferrite of excellent l/aQ characteristics.

The variation in a at 3 rnilli-oersteds and 100 kc. of the presentferrite, is shown in FIG. 9. As seen in FIG. 10, which shows the case ofadding silicon dioxide only to the same main composition, quite a slightaddition of silicon dioxide causes increase in a, contrary to the resultillustrated in FIG. 3, which shows a case of adding calcium oxide onlyto the same composition. In a case where a combination of calcium oxideand silicon dioxide is added, deterioration in p. due to calcium oxideis prevented by the presence of silicon dioxide, where the addition ofcalcium oxide is less than 0.2%. It is, therefore, possible inaccordance with the present invention, to maintain a comparatively highpermeability and also to obtain a high value of Q, as mentionedpreviously.

As shown in FIG. 11, which shows variation in the value of l/ Q of thepresent ferrite of the invention, it will be evident that the ferrite ofthe present invention is superior to that of FIG. 4, which shows a caseof adding calcium oxide only to the same main composition of maincomponents, or to that of FIG. 12, which shows a case of adding silicondioxide only thereto.

It has also been found that in a manganese-zinc ferrite containingcalcium oxide and silicon dioxide, with less than 0.05% of calcium oxideand less than 0.005% of silicon dioxide do not give appreciableimprovement;

more than 0.3% of calcium oxide results in large hysteresis loss, andmore than 0.035% of silicon dioxide results in large crystal size, poor1/ nQ, and sudden deterioration of the hysteresis loss.

The present invention is effective not only in the abovementionedcomposition, but also to compositions differing therefrom. Table 2 showsvariations of Q, and l/ tQ, when adding 0.1% calcium oxide only, 0.02%silicon dioxide only, and 0.1% calcium oxide plus 0.02% silicon dioxide,respectively, to a ferrite of the composition consisting of 53.5 molpercent ferric oxide, 30 mol percent of manganese oxide, and 16.5% ofzinc oxide. As shown in this table, similar results can be obtained evenif the fundamental composition be varied.

6 Table 4Continued Table 2 Addition Additive Char- CharacteristicsCondition actor- (3110, 0.1 S101, 0.02 020,01 istics (32.0, 0.1 $101,0.01 020, 0.1weight None percent percent percent Sioz, None weight;weight percent; SiO

0.02 percent percent percent 0.01 Weight percent 2, 200 2, 100 2, 300 2,200

4. 3 25 40 110 2, 450 2, 300 2,700 2, 450 s 19 10. 8 4. 1 5 32 24 87 2,150 2, 050 2, 450 2, 200 4 29 85 1, 500 1, 450 1, 780 1, 550 1 7 4 6 1 93 7 00 1 00 0 1, 50 Table 3 shows a series of different compositions of7 42 :34 102 manganese-zinc ferrites to which either 0.1% of calcium200(5) :22 3% 8g oxide or 0.01% of silicon dioxide, or both, have been1,950 1,900 2,200 2 added. Table 4 shows the effect of sintering each of1,50% 53 3% 8 these different compositions in a pure nitrogen atmos- 1 31 58 1 3% 1 3 phere at 1200 C. for four hours, followed by cooling 8 idown to 400 C. in nine hours, followed by abrupt re- 2 33 g? ,18? movalinto air of normal temperature. 1, 200 1,150 1, 250 1 200 5 30 26 001,200 1, 150 1, 250 1,200 1 8 1 50 1 46 1 58 ,55 450 700 6 Table 3 0 40as 111 Composition g gg 9S8 1, 150 1, 100 1, 200 1, 150 Sample No. MnO,mol 1 9203, 11101 Z110, mol 5 28 110 percent percent percent;

2s 52 23 30 3; 2i The data of Tables 3 and 4 establish that throughout3; g? the Wide ranges of variation of the basic manganese-zinc 27 g 20ferrite compositions, the desired effect of increased perg; 2% i3meability and decreased hysteresis losses remains un- 29 52 19 35changed, in contrast with the effect of only the calcium 29 53 18 oxideor only the silicon dioxide addition. Furthermore, 29 54 17 29 55 16 thedeslrcd effect or increased permeability and decreased 3} g hysteresislosses over this wide range of manganese-zinc 31 54 15 ferritecompositions is retained even if their sintering cong g3 4O dition ischanged. For example, a manganese-zinc fer- 33 55 14 rite compositionconsisting of ferric oxide 53.5 mol per- 33 54 13 cent, manganese oxide30.0 11101 percent, and zinc oxide 33 55 12 35 52 13 16.5 mol percent,was combined with three different addigg i3 tions of either 0.02%silicon dioxide, or 0.1% calcium 37 52 11 oxide, or with both 0.02%silicon dioxide and 0.1% 37 53 10 calcium oxide, and each of these threedifferent ferrite 37 54 9 37 55 8 compositions was sintered under eachof the following series of different sintering conditions:

Table 4 O Additive Hours C d Char- 011 ition actera 2 0 1 0001 d to 4000. for 9 istics 09.0, 0.1 S101, 0.01 CaO, 0.1we ight 1 mggiwi l t 1, 0031 5 nd t en 111 None weight weight percent; S1O2, into the m p epercent weleht 2 do 1, 200 4 Cooled to 200 o. for 13 percent hours andtaken out infodthe air3 C I 17 3 d0 1.200 4 0000 to 10 or 3,050 2,8003,450 3,250 hours and taken out 4 25 20 61 into the air 3,750 3,5004,050 3,600 0 4 do 1,200 2 Cooled to 400 0. for 9 3 18 14 55 hours andtaken out 2, 700 2, 500 3, 000 2,700 into the am 3 16 12 52 10 1,200 6Do. 1,800 1,700 2,000 d 1,220 4 Do. 3 14 12 Pure nitrogen atmos- 1.250 4Do. 2, 800 2, 050 3,200

30 Nitrogen atmosphere 1,200 4 Do. 3, 35(3) 22 containing 0.2% ox- G11.2 50 2,300 2,700 0 9 Yin, 1,200 4 0001811 to 100 0. in 17 20 15 63 hoursand taken out 3 9g %2 gg into the air.

10 Nitro en atmosphere 1 200 4 Do. 2 2 .831 1 3 containing 0.4%,0x-

ygen. 3 100 2, 000 3,450 3 000 4 27 18 1 11 do 1,250 4 Do 2, 400 2, 2502, 700 2, 400 4 24 17 05 1, 000 1, 500 1, 850 1, 050 4 24 17 57 K Mug 3g28 38 7 5 Table 5 below shows the effect on the permeability andhysteresis losses of these three different ferrite compositions causedby each of the series of different sintering the effect of the combinedaddition of the present invention is.

Table 7 a at 3 mil- Q at 3 milllnQ at 3 milli- Hm at 1030 B at 40 mil-All/[i l o lioersted, lioersted, oersted, 100 kc. millioersted, 100liocrsted To (C) (0-40C 100 kc. 100 kc. kc.

2, 150 210 2. 2x10 250x 4, 700 230 S 10- conditions: 10 In Table 7, Esdenotes magnetic flux, Tc the Curie Table 5 point, and A,'.L/, C. therate of change of permeability per unit and unit temperature difference.Additive It is to be understood that in adding calcium oxide andCharsilicon dioxide to the main components of a manganese- None gg gg gf2 l5 zinc ferrite, any compounds of calcium and silicon may percentpercent 0.01 weight be used, as long as they are salts that becomecalcium Percent oxide and silicon dioxide in the final sintering stage.Also, the additions may be combined at any stage of the 1 a 19% 22 28298 ferrite'forming process as long as it is prior to the final 2 it2,350 2,150 2, 500 2,350 sintering stage. 3 g 3% 2, 23 183 It should beunderstood that the symbols used for desig- Q 4 24 35 100 hating thecharacteristics of the ferrite compositions de- 4 E; 2 2 8? 22 503scribed herein, have their conventional meanings, namely, 5 I-" 2,3502,200 2, 500 2,4 0 t means the permeability; Q means the ratio of thein- 6 8 35% 28 %?8 25 ductive reactance to the effective seriesresistance; kc Q -9 22 7 95 means the frequency of the alternatingcurrent in kilo- 7 E; '592 8 2? 32 cycles per second; H means the fieldstrength. 3 I 21200 2,100 2,350 2,250 It will be apparent to thoseskilled in the art that the 9 8 230(5) 53 novel principles of theinvention disclosed herein in con- Q 4.? 42 122 30 nection with specificexemplifications thereof, will suggest 10 a 2,200 2,100 2, 300 2,200 A QQ2 4 59 202 various other modifications and applications of the same. Itis accordingly desired that in construing the breadth Although thepermeability and hysteresis loss characteristics of these ferritecompositions are affected by the sintering condition, the effect of thesintering conditions is minimized for ferrite compositions of theinvention containing combined additions of silicon dioxide and calciumoxide. In other words, the unique, desirable effect of the combinedspecified addition of both silicon dioxide and calcium oxide to thespecified manganese-zinc ferrite composition, is substantiallyunaffected by changes in sintering conditions.

Although it has been known to add oxides of aluminum, tin, and titaniumfor the purpose of improving the temperature coefficient of permeabilityof manganesezinc ferrites, the effect of the present invention isunaffected by the existence of these added materials. For example, theeffect of the combined additions of the present invention for a ferritehaving the composition, ferric oxide 54 mol percent, manganese oxide 35mol percent, and zinc oxide 11 mol percent, with the further addition of0.5% of titanium oxide, is as shown in Table 6 below:

Table 6 Addition Clmracter- Ti Oz, 0.5

istics Ti02, 0.5 TiOz, 0.5 percent TiOg, 0.5 percent percent (3210, 0.1

percent 0210, 0.1 510:, 0.02 percent,

percent percent SiOz, 0.2

percent u 1, 700 1, 700 1,850 1, 800 Q 25 45 170 1/pQX10 23.6 13.2 13. 53. 3

Thus it is possible to manufacture manganese-zinc ferrites of excellentquality by suitably adjusting the quantity of addition materials,sintering atmosphere, and sintering temperature. For example, thecharacteristics of a manganese-zinc ferrite having the compositionferric oxide 54.1 mol percent, manganese oxide 35 mol percent, zincoxide 11.9 mol percent, to which 0.6% stannic oxide, 0.1% calcium oxide,0.26% silicon dioxide, are added, and which is sintered at 1250 C. forfour hours in an atmosphere of nitrogen containing 0.4% oxygen, areshown in Table 7 below. It will be evident from this how great of theappended claims, they shall not be limited to the specificexemplifications of the invention described herein.

We claim:

l. A sintered manganese-zinc ferrite composition consisting essentiallyof 52 to 55 mol percent of Fe o 25 to 37 mol percent of MnO and 23 to 8mol percent of ZnO, and also combining the two additions consisting of0.05 to 0.3% by weight of calcium oxide and 0.005% to 0.035% by weightof silicon dioxide, whereby the permeability and hysteresis losses ofsaid ferrite composition are materially increased and decreased aboveand below, respectively, the permeability and hysteresis losses of thesame composition containing only one of said two additions.

2. A sintered ferrite composition as claimed in claim 1, containing atmost 001% by weight of impurities.

3. A sintered ferrite composition as claimed in claim 1, containing atmost 0.5 by weight of TiO:,.

4. A sintered ferrite composition as claimed in claim 1, containing atmost 0.6% by Weight of stannic oxide.

5. A sintered ferrite composition as claimed in claim 1, containing atmost 0.5% by weight of TiO;, and at most 0.6% by weight of stannicoxide.

6. In a process of making a ferrite of minimum magnetic retentivity andlow hysteresis losses as measured by l/nQ of such ferrite, the stepscomprising preparing a mixture of ferrite ingredients which uponsintering form a ferrite composition consisting essentially of 52 to 55mol percent of Fe O 25 to 37 mol percent of MnO and 23 to 8 mol percentof ZnO, and also containing two addition ingredients which in thesintered ferrite consist of 0.05% to 0.3% by weight of calcium oxide and0.005% to 0.035% by weight of silicon dioxide, and sintering the mixtureof all these ingredients in a neutral gas atmosphere at temperatures inthe range of 1200 C. to 1250 C.

References Cited in the file of this patent UNITED STATES PATENTS2,903,429 Guillaud Sept. 8, 1959 2,924,573 Sasaki et al. Feb. 9, 19602,992,990 Parker July 18, 1961

1. A SINTERED MANGANESE-ZINC FERRITE COMPOSITION CONSISTING ESSENTIALLYOF 52 TO 55 MOL PERCENT OF FE2O3, 25 TO 37 MOL PERCENT OF MNO AND 23 TO8 MOL PERCENT OF ZNO, AND ALSO COMBINING THE TWO ADDITIONS CONSISTING OF0.05% TO 0.3% BY WEIGHT OF CALCIUM OXIDE AND 0.005% TO 0.035% BY WEIGHTOF SILICON DIOXIDE, WHEREBY THE PERMEABILITY AND HYSTERSIS LOSSES OFSAID FERRITE COMPOSITION ARE MATERIALLY INCREASED AND DECREASED ABOVEAND BELOW, RESPECTIVELY, THE PERMEABILITY AND HYDTERSIS LOSSES OF THESAME COMPOSITION CONTAINING ONLY ONE OF SAID TWO ADDITIONS.